YB1211 Datasheet, PDF (7/9 Pages) YOBON TECHNOLOGIES,INC. – 300mA External Adjustable LDO Regulator

YB1211
300mA External Adjustable LDO Regulator
Functional Block Diagram
Functional Description
The YB1211 is an low-noise, low-quiescent
current, low-dropout linear regulator. It is
supplied in a small SOT-25 package for
different applications. YB1211 can supply
loads up to 300mA (typical operation, not
maximum) and the output voltage are
adjustable by a pair of resistor net (R1 and
R2 in Figure 3), ranging from 1.22V to 5.0V.
As shown in the Functional Block Diagram,
the YB1211 consists of a reference and
an error amplifier, a big output drive
transistor, thermal sensor, and short circuit
current limiter. The feedback voltage is
acquired from the external voltage divider
through pin ADJ.
The internal reference is connected to the
error amplifier’s inverting input. The error
amplifier compares this reference with the
feedback voltage and amplifies the
difference. If the feedback voltage is lower
than the reference voltage, the gate of the
pass-transistor is pulled low. This allows
more current to pass to the output and
increases the output voltage. If the
feedback voltage is too high, the gate of the
pass transistor is pulled high, allowing less
current to pass to the output.
Stability
The YB1211 is a high performance LDO
emphasizing stability with low output
capacitance. It is able to maintain stability
with an output capacitor as low as 1.0 uF.
The output capacitor can also be increased
to optimize performance. The YB1211 will
remain stable and in regulation with no load,
unlike many other voltage regulators.
Internal P-Channel Pass Transistor
YB1211 MRev. 1.0
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